In a standard pleated shade construction, a piece of material is prepleated into a plurality of horizontal sections which stack one on top of the other when the shade is in its raised position. Alternate pleats face toward the front and rear of the shade. Each section has at least one hole punched through the center thereof which holes are aligned when the shade is folded. Normally, there would be two or more aligned rows of holes formed in the shade sections. Cords passing through the aligned holes are utilized to control the raising and lowering of the shade and to maintain the accordion stacks.
One problem with this construction is that short segments of cord are visible in each of the forward-facing pleats of the shade when the shade is in its lowered position. In some applications, the appearance of these cords is not aesthetically acceptable. A more serious problem is the holes in the shade sections which pass bright light rays during the day and which permit room light to be seen and reduce privacy at night. Another problem with having cord holes is that they reduce the insulating effect of the shade. Further, while the standard pleated shades, particularly ones having a metalized layer, provide some level of insulation, they are of only limited value as a vapor barrier.
Another limitation with existing pleated shades is that it is virtually impossible to repair a portion of a large shade which is defective or has become damaged by splicing in a replacement section, a capability which is desirable in large shades, and it is virtually impossible to splice together two sections of shade to achieve a shade of a desired length, forcing shades to be cut to custom lengths, or to achieve a desired aesthetic effect.
An ability to easily and inexpensively splice shades would also reduce production costs by permitting flaws to be cut from pieces of material and the cut ends spliced, thereby minimizing material wastage. Finally, it is now difficult to fit a shade to an opening which is wider than standard bolt widths. By pleating along the length of the bolt, a shade of any desired width could be fabricated, with the desired length achieved by splicing.
While some of the problems discussed above are overcome by existing honeycomb shades which are formed by securing together cylinders of the desired material which have opposed creases preformed therein, these shades are relatively complicated and expensive to manufacture and are not adapted to the requirements of certain applications.
Another approach to providing a pleated shade without cord holes and without visible cords is to in some manner provide a tab extending behind each rear pleat with the cord holes being formed in such tabs. This construction however results in the cords being positioned behind the center of gravity of the shade. This and other factors result in such shades experiencing a phenomenon known as "pleat reversal" wherein one or more front or nose pleats open and move toward the cord while the rear projected tabs become almost parallel to the cords This phenomenon can occur whenever, as a result of various forces exerted on the shade and tabs, certain tabs are caused to assume an angle of approximately 45.degree. or greater to the horizontal. Substantial difficulties have been experienced in designing relatively small pleated shades, for example shades having approximately a one inch pleat, which do not experience this pleat reversal phenomenon.